What group followed the cattlemen to the area, and what did they do

Cattlemen were replaced by wheat farmers, who settled in the Great Plains and over-plowed the land.

Explanation:

The Great Plains had rich, fertile, prairie soil that had taken thousands of years to build up. Following the Civil War, cattlemen over-grazed the semi-arid Plains, overcrowding it with cattle that fed on the prairie grasses that held the topsoil in place.

Cattlemen were replaced by wheat farmers, who settled in the Great Plains and over-plowed the land.